This invention relates to improved methods for making silicone-organic copolymers. More particularly, the invention relates to methods for making silicone-organic copolymers with molecular weight control and without the need for protecting groups on organofunctional silicone intermediates.
Silicone-organic copolymers are widely used, notably in the preparation of personal care products. Methods currently known in the art for making these copolymers are often cumbersome, time consuming and expensive, if they work at all, as a great deal of care must be taken to insure that the properties of these materials meet the rigid specifications usually required, including high clarity and optimal strength. Industry is constantly seeking new materials in this class and improved ways of preparing them.
A recent effort in this regard is disclosed by Barr et al. in U.S. Pat. No. 6,051,216 and in the corresponding PCT Publication No. WO 99/06473. Siloxane based polyamides useful as cosmetic gelling agents are described therein, as well as methods to make these polymers. The methods therein have been found to be less than cost effective in most cases given the large number of difficult steps involved. For example, it is necessary to have protecting groups on some of the organofunctional siloxane intermediates that later have to be removed.
U.S. Pat. No. 5,981,680 to Petroff et al. is directed at an improved process to make the polyamides of Barr. Instead of reacting a protected organic acid with a siloxane before forming the amide linkage as in Barr, Petroff calls for forming the amide linkage before any reaction with siloxane, thus eliminating the necessity of using protecting groups.
A need still exists, however, for new silicone-organic copolymers and further improved methods of making silicone-organic copolymers. In particular, a need exists for new silicone-organic copolymers that have very specific molecular weights or ranges of molecular weights and for improved methods of making silicone-organic copolymers with molecular weight control. The present invention is directed to filling these needs.
It is an object of this invention to provide methods to make silicone-organic copolymers with molecular weight control. Thus, this invention relates to a method for making silicone-organic copolymers comprising: copolymerizing an organic component other than a diamide with a silicone component, where, at least a portion of at least one of these components has been processed as to chain terminators individually, or at least a portion of both components has been processed together as to chain terminators, such processing taking place at any point prior to completion of copolymerization.
The invention also relates to a method for making siloxane-based polyamides comprising: copolymerizing, in the presence of a catalyst, an SiH containing siloxane and a vinyl containing diamide in a combination in which the molar ratio of total chain terminators added to that of total pure diamide added is 1:99 to 3:97 and the molar ratio of total siloxane SiH added to total diamide vinyl added is 0.9:1 to 1.1:1.
Also in this regard is a method for copolymerizing silicone and organic reactants into a copolymer with molecular weight control, the method comprising: estimating a total amount of polymerization chain terminators needed to produce the copolymer of desired molecular weight under reaction conditions via a system model, processing at least a portion of at least one individual copolymerization reactant or at least a portion of a mixture comprising some or all copolymerization reactants such that the total amount of chain terminator present under reaction conditions is as estimated, and copolymerizing the silicone and organic reactants under reaction conditions. Further in this regard is a method for making silicone-organic copolymers in a reaction system with molecular weight control, the method comprising: providing a copolymer molecular weight set point to a model based controller, using the controller to determine a value for a variable or values for a set of variables corresponding to an effective amount of chain terminator in the reaction system and affecting a change or changes in the system with the aim that the value for the variable or values for the set of variables determined by the controller be obtained.